228 



existing Shelf sites would impose severe economic burdens, surveillance 

 and monitoring difficulties, and logistics problems" (EPA 1980, p. 5-24). 



Water Qua! ity 



Because of its distance from anthropogenic coastal inputs, water quality 

 at the 106-Mile Site is similar to that of the open ocean. The highly 

 dispersive nature of the area combined with the large volume of available 

 dilution water suggests that sewage sludge disposal at the site would not 

 result in contaminant concentration increases in the water column, other 

 than transient increases immediately following each dump (Section 7.6). 



Sediments and Benthos 



In comparison to the 12-Mile Site, few data exist on concentrations or 

 distributions of metals or organics in sediments in or near the 106-Mile 

 Site. Since sewage sludge is not expected to reach the bottom in any 

 significant amount, a conclusion reached in the 1980 FEIS and supported 

 by more recent data (Section 9.6), it is unlikely that the sediments of 

 the 106-Mile Site would be contaminated as a result of sewage sludge 

 dumping. However, the paucity of baseline sediment concentration data 

 from the 2,500 square kilometer area will make it difficult for 

 monitoring programs to accurately assess the extent of any such 

 contamination. 



If sewage sludge dumping takes place on a routine continuing basis at the 

 106-Mile Site, it is possible that some sewage sludges will be dewatered 

 for transport and disposal at the site. Such dewatering processes could 

 produce sewage sludge with a greater tendency to sink through the water 

 column, and an undetermined portion of the sewage sludge dumped might 

 reach the sediments (Section 9.6). The 1980 FEIS did not address this 

 possibility, and little or no relevant data on the behavior of dewatered 

 sludges in the ocean appear to exist. 



Because of the demonstrated rapid dilution and dispersion processes at 

 the 106-Mile Site, and the conclusion that sewage sludge particles dumped 

 at the site are not expected to reach the bottom in any significant 

 amounts, impacts on benthic populations are expected to be negligible 

 (Section 14.2). Furthermore, since the natural surficial sediments at 

 the site consist predominantly of sandy-silt and clay mixtures (Section 

 9.2), any particles that did settle out would not significantly alter 

 the physical environment of the benthos. The predicted lack of benthic 

 impacts is consistent with Agency observations of no benthic community 

 effects, even after years of waste disposal at the 106-Mile Site 

 (Sections 14.1 and 14.3). 



Oxygen Depletion 



Significant reductions in dissolved oxygen as a result of sewage sludge 

 dumping would not occur at the 106-Mile Site, due to the depth of the 

 water column and the very large dispersion capacity inherent in the water 

 masses present. Similarly, the technical literature indicates that the 

 transfer of sewage sludge disposal activities from the 12-Mile Site would 

 not reduce either the frequency or severity of periodic anoxic conditions 



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